I think he has been using illegal substances until probably the Martinez fight. This guy sheds a ton of weight and is a lazy ass, so there's a possibility he's been using diuretics (possibly the same one he was caught using).

The Rubio fight, as previously mentioned, was also a HUGE indication. I mean how does a prestigious (lol?) sanctioning body such as the WBC "forget" to do a post fight drug test? How stupid do they think people are to give such a lame and amateur excuse?